Vehicles are provided with a seat belt and a seat belt retractor. Once the seat belt has been extended or unwound and a tongue is engaged into a latching or buckle device, it is desirable to retract or wind up the excess amount of the seat belt.
Vehicle seat belts are also provided with an automatic winding device that, upon sensing of a predetermined condition will wind up a predetermined amount of slack or amount of seat belt webbing during a predetermined activation event (e.g., a massive deceleration or vehicle conditions sensed before an accident). This device employs a motor, which is energized to wind up the seat belt. In addition, seat belt retractors are also equipped with an automatic locking retractor (ALR) or an emergency locking retractor (ELR) or a combination (switchable) ELR/ALR retractor 12, which will lock the seat belt retractor up (e.g., prevent further pay out of the seat belt webbing) when there is an abrupt pulling (tension) on the belt sensed by a web sensor or there is activation of a G sensor, which in combination of G sensor activation and web payout will cause lockup of the seat belt retractor. In either occurrence, there will be a lockup of the seat belt retractor. In order to unlock ELR/ALR retractor the tension upon the seat belt must be removed, and in the case of activation by a G sensor, the sensed condition must no longer exist.
During operation, a pretension signal will be sent to a motor of the motorized retractor to retract a portion of the seat belt when an imminent danger or predetermined condition is detected. In addition, this predetermined condition is also likely to activate either the G sensor or the web sensor. Upon receipt of the pretension signal, the motorized seatbelt retractor will respond by quickly tensioning the belt to a predetermined level and thereafter a pyrotechnic pre-tensioner and inflatable cushion deployments will follow if an event (e.g., collision) occurs. Some of the features of a motorized seatbelt retractor are: it removes seat belt slack when an imminent danger is detected; and the motorized seatbelt retractor will pull and hold an occupant in a designated position prior to the collision occurring. In addition, the motorized seatbelt retractor is configured to work in harmony with a pyrotechnic pre-tensioning device in order to maximize the distance between the belted occupant and other parts of the vehicle.
If the imminent danger is avoided and no longer present (e.g., collision avoided), the motorized seatbelt retractor is configured to reset itself and remain on a standby mode for the next pre-tensioning signal. However and during this same sequence of events, the ELR/ALR retractor may have locked up due to a quick seat belt web payout or web payout when a G sensor is activated. In addition, a clutch of a gear train of the motorized seatbelt retractor will also become engaged at the beginning of the pretensioning cycle. Moreover, the lock up of the ELR/ALR retractor and the clutch of the motorized seatbelt retractor will keep the tension on the seatbelt and the occupant. As discussed above, this lockup can be initiated by: activation of the web sensor when the seatbelt is subjected to a quick web payout or activation of a G sensor during a G event (above approximately 0.5 G) and where there is relative movement between the web spool and lockup wheel, which is caused by seat belt web payout during the activation of the G sensor. Accordingly, the lockup occurs when the predetermined conditions are sensed and there is seat belt webbing payout. Thus, there is need to provide a means to unlock the belt if the predetermined event is no longer occurring or passes.
One method employed to provide an unlock feature for motorized seatbelt retractors is to provide the motorized retractor with a quick but relatively high burst of current at the end of the pretensioning cycle wherein there has been a lockup of the ELR/ALR retractor. This burst of current will cause the web to pay-in further due to the movement of the gear trans by the motor, which in turn causes a relative-movement between the web spool and lockup wheel. This relative movement will in turn reset the lockup sensors, which in turn unlocks the retractor, and thus returns the webbing to a comfortable tension. However, this method of unlocking of the lockup sensors may not be favorable in that it requires additional tension to be applied to the seat belt that is already in a tensioned state. In other words, and in order to unlock the device, the seat belt webbing has to be pulled in further when it is already in a tensioned state. This additional tension is often referred to a “Second Stroke” phenomenon. In addition, the clutch of the motorized gear train may also need to be unlocked after this sequence via reversal of the motor (e.g., driving the motor in an opposite direction).
Accordingly, it is desirable to provide an apparatus and method for unlocking the motorized retractor after the same has been locked in accordance with a predetermined event (e.g., imminent danger, high G forces, high tension e.g., web payout) and the condition or sensed event passes without the activation of a second system (e.g. inflatable cushion, pyrotechnically activated pretensioning device). Moreover, it is also desirable to provide such an apparatus that has a retractor that locks up only when predetermined tensions or forces are applied during or after motorized retraction.